Dianne J. Luning Prak, Jim S. Cowart
High Resolution Image Download MS PowerPoint Slide The combustion behavior of fuels or surrogate fuel mixtures can be modeled better if their physical properties are known. This work reports densities, viscosities, and speeds of sound of binary mixtures of undecane with n -alkylbenzenes (ethylbenzene to n -tridecylbenzene). An assessment of mixture densities using jet and diesel fuel specifications shows that some of these mixtures fall within the required range of values. Mixture densities and speeds of sound decreased with increasing temperature and decreasing n -alkylbenzene mole fraction. Mixture viscosities decreased with increases in temperature and the component with lower viscosity, except for some n -butylbenzene systems where smaller viscosities were found in a mixture. Increasing the n -alkylbenzene size up to n -tridecylbenzene produced lower excess molar volumes ( V m E ’s) and excess isentropic compressibilities as well as higher excess speeds of sound. Viscosity deviations were the lowest for the n -hexylbenzene mixtures. A reduction in free volume is likely a contributor to negative V m E ’s, while a reduction in the attraction of molecules is likely a contributor to the positive V m E ’s. A comparison of derived properties with those of undecane/ n -alkylcyclohexane mixtures revealed similar trends, with the greatest differences occurring for the smallest molecules.